Flash memory bears little resemblance to a magnetic recording system. Commodity flash chips are closed systems with no external access to analog signals, in sharp contrast to the typical Hard Disk Drive (HDD) where analog signals have always been available for detection. Even though the HDD is a complex electro-mechanical system and can suffer catastrophic failure, it has been possible to engineer drives to have a life expectancy with little to no degradation in performance, which extend beyond their time of technical obsolescence. The data reliability of flash memory, on the other hand, is known to degrade through the life cycle and therefore has a finite life. Consequently, when flash memory was first conceived as a memory device the target error rate at the output of the chip has been kept very low, as opposed to systems where stronger Error Correction Coding (ECC) may be used at the onset, like deep space communications.
Lower priced Solid State Drives (SSD) are typically manufactured using multi-level cell (MLC) flash memory for increased data capacity, but MLC has less data reliability than single-level cell (SLC) flash memory. Consumer SSD manufacturers have mitigated such problems by employing interleaving and/or providing excess capacity in conjunction with wear-leveling algorithms and/or limiting the amount of data the user can write to the device. MLC flash endurance, however, requires sophisticated algorithms to make them acceptable for enterprise SSD applications where mission-critical data is stored.